The uniting of the opposition in 2023 was a moment of optimism built out of despair. Labour, the Lib Dems, Greens and Welsh Nationalists resolved to do whatever it took to drive Boris Johnson from power. Under the slogan “just get rid of them”, they overcame an electoral system that had delivered a majority of 80 to the Conservatives on 43% of the vote in 2019 and could do so again. In Turkey, Hungary and Israel, opposition parties had shown that protecting democracy from strongman leaders was more important than ideological divisions. The UK centre-left did not want its country to become a one-party state either and decided to put just one opposition candidate against the Tories in each seat. Such thoughts are fantasies today. Suggest opposition parties work together to stop a stagnant and autocratic Conservative regime stretching from 2010 to 2028 and beyond and harrumphing commentators wag their fingers. To claim there is an anti-Conservative majority because 57% of the electorate did not vote Tory is tendentious, they say. One could as easily say there was a 68% anti-Labour majority at the 2019 election because only 32% voted for Jeremy Corbyn. Evidence going back to the 1980s shows many who vote Liberal would, if forced to choose, prefer the Conservatives to Labour. Progressive alliances are unsporting and un-British, they continue. Voters would smell a stitch-up. In any case, what would a coalition of opposition parties do about Scottish nationalists? The SNP has every interest in keeping Johnson in power because he drives Scottish voters into its arms. It does not want a better UK, but for Scotland to leave the UK. I accept that these arguments were true in 2019, but the liberal-left thinktank Best for Britain is making a persuasive case to opposition leaders that they are not true now. It used the most accurate available polling methods to test how an electoral pact would work in every English constituency. It found that, if their preferred party did not stand, 41% of Lib Dem voters would back Labour, with 19% saying they would vote Tory. Similarly, Labour supporters were almost twice as likely to vote for the Lib Dems (40%) than the Conservatives (25%). About one-third of Labour and Liberal Democrat voters would transfer to the Green party, which supported the conclusion that a unity candidate could beat the Conservative in many marginal seats. The findings should only surprise those who haven’t been paying attention. Polling earlier this year found two-thirds of voters believed parties that broadly agree with each other should co-operate in elections. (Who knew?) Meanwhile, 60% of voters do not know who came second in their constituency. They needed politicians to show leadership by offering them a unity candidate rather than assume they can work out how to vote tactically themselves. As for the notion that the British would reject a pact as unsporting, Nigel Farage stood down candidates in Tory-held seats in 2019 and will doubtless do the same in 2023 or 2024 if he revives his movement. The centre-right plays the electoral system by operating as a united bloc, to the demonstrable advantage of the Tory party. I can find no reason why the centre-left shouldn’t follow suit, unless it subconsciously wants to lose, which, judging by its behaviour, is a possibility you should never dismiss. Alliances are springing up everywhere as reactions to democratic emergencies. Ünal Çeviköz, a former Turkish ambassador to London and a leader of the Republican People’s party, summed up the spirit of opposition solidarity when he told me the true dividing line in modern politics was not between left and right but democrats and autocrats. Six opposition parties are co-operating to oppose Recep Tayyip Erdoğan as the manic Turkish leader wrecks the economy, neuters the judiciary and keeps thousands of political prisoners in jail. The struggle to stop Benjamin Netanyahu has produced a coalition government in Israel that upends everything you thought you knew about the Middle East. The Islamist Arab List co-operates with the Jewish ultranationalist Yamina (“Rightwards”) party. Fear of Netanyahu’s return keeps them and disparate parties of right and left together. In Hungary, the united opposition against Viktor Orbán’s corrupt control of the state and media runs from the Greens and the socialists through to the formerly neo-Nazi Jobbik party, which is now a Hungarian version of Ukip. Your enemy’s enemy is your friend when the future of the democratic system is in the balance. A united centre-left slate here would not have to struggle to cover a gaping ideological divide. If it cannot include the SNP, so be it. The biases of first past the post benefit Scottish as well as Brexit nationalists and co-operation between Labour and the Lib Dems could stop a repeat of the SNP winning 48 out of 59 Scottish seats in 2019 with just 45% of the vote. Caroline Lucas, of the Green party, favours an anti-Tory front. We are “out of time” on global warming, she says, and do not “have the luxury” of indulging tribalism for another election cycle. The Lib Dem, Layla Moran, says opposition parties must work together against a “nativist government [that] is attacking our rights, trashing our reputation abroad and has cost thousands of lives by mismanaging this pandemic”. Most other Labour and Liberal Democrat leaders remain cautious. Naomi Smith, Best for Britain’s CEO, is trying to help them help themselves. She has identified 25 seats where the Lib Dems or Greens could win if Labour gave them a free run and accepted proportional representation as part of the deal. In return, the Lib Dems and Greens would stand down in 150 seats, which strikes me as a decent offer. In all likelihood, the narcissism of small differences and the conservatism of the British centre-left will prevent co-operation. But before politicians and their supporters reject it, they should ask the old question: if not now, when? Will they change their minds and accept that a radical realignment is needed after the Conservatives fifth election victory in 2023 or 2024 or sixth in 2028 or 2029? For how much longer will they be able to say that they oppose the Tories without doing what needs to be done to eject them from power? Nick Cohen is an Observer columnist